Personal opinion only here...
Unless otherwise defined (in a version containing the written approval of the CAA):-
"Maintenance Base" = an airport at which the airline has a maintenance facility, whether their own or 3rd. Party.
A company attempting to define "Maintenance Base" as the maintenance area only is, IMHO, very far indeed from the intention of the MEL and the spirit of the law.
Further "...where repairs may be carried out" does not mean to limit the MEL further - spares, manpower, etc etc being temporarily unavailable do not permit the aircraft to continue. Otherwise I could see the scene:- "G-XXXX is coming in with that snag - quick - five of you guys take an early lunch so it can depart again!"
If either of these were to be used by airlines as excuses I would expect the CAA FOI to come down very hard, and demand a change to the wording of the MEL to close such a loophole.
Misuse of an MEL in this way is, IMO, dangerous and not to be condoned.